A construction method for an integrated model of deepwater high-temperature and high-pressure fracturing and packing based on wellbore / formation coupling

Abstract

The present invention relates to a method for constructing an integrated model of deepwater high-temperature and high-pressure fracturing and gravel packing based on wellbore / formation coupling. The steps are as follows: constructing a fracture propagation and extension model; constructing a fracture filtration model; constructing a wellbore and fracture temperature field model; constructing a wellbore gravel packing model; constructing a pumping program design model. When modeling, the present invention couples the wellbore gravel packing and the formation fracturing process through pressure, temperature and flow rate, and further realizes the integrated modeling of the fracturing and gravel packing process through the data flow transmission between each model; when constructing the fracture propagation and extension model, the width equation, height equation, pressure drop equation and continuity equation are effectively combined, and are processed based on the cohesion model for different formation conditions. The present invention can simulate the entire process of fracturing and gravel packing such as the flow of fracturing fluid in the wellbore, the propagation pattern of formation fractures, and gravel packing, and has the advantages of comprehensive coverage, accurate simulation, and strong versatility.

Description

Technical Field

[0001] The present invention relates to the technical field of oil development, and particularly to a method for constructing an integrated fracturing and gravel packing model for deep-water high-temperature and high-pressure reservoirs based on wellbore / formation coupling. Background Art

[0002] During the process of offshore oil and gas development, sand control is a great challenge, and gravel packing sand control is a commonly used sand control method. Although the in-tube gravel packing method has good sand control effect, it also increases the seepage resistance of reservoir fluids flowing into the wellbore and reduces the productivity. In order to overcome the deficiencies of downhole gravel packing completion and improve the overall productivity level, the fracturing and gravel packing sand control technology is proposed. This is a new composite sand control technology that combines hydraulic fracturing and gravel packing for medium and high permeability formations, organically integrating the two processes and concentrating on their technical advantages to achieve the best effect of high production and sand control in oil wells, which cannot be achieved by traditional sand control processes.

[0003] After fracturing and gravel packing, crude oil linearly seeps from the formation into the fractures and then from the fractures into the wellbore. Not only does the seepage area increase significantly, but also the drilling and cementing damages are eliminated (or partially eliminated), and the perforation compaction damages are completely eliminated (or partially eliminated). This is the principle of productivity increase by fracturing and gravel packing. The fracture support zone has a good mechanical bridging effect on formation particles. During the process of formation fluids flowing into the wellbore, the reservoir sand has to pass through three barriers. First, it is blocked by the gravel supported in the fractures, then by the gravel layer in the wellbore annulus, and finally by the screen pipe. Through these layers of blocking, sand-free high production can be achieved, and at the same time, the well life is extended. This is the principle of sand control by fracturing and gravel packing.

[0004] In recent years, a considerable part of oil fields in China have successively adopted the fracturing and gravel packing process for sand control, but most of them are based on process research with less mechanism research and large errors based on empirical judgment. The existing fracturing and gravel packing models and methods have poor generality and applicability to different reservoir conditions and environments. In view of the fracturing and gravel packing construction requirements for deep-water high-temperature and high-pressure reservoirs, it is necessary to construct a fracturing-packing integrated simulation method considering the influence of high-pressure temperature change to solve the numerical dynamic simulation problem of the whole process of fracturing and gravel packing (from fracturing initiation, fracture extension, swelling, to in-tube α forward packing and β reverse packing), and realize the optimized design of fracturing and gravel packing to effectively guide the development of fracturing construction. Summary of the Invention

[0005] Aiming at the problems that there is no full-process model combining fracturing and gravel packing with wellbore gravel packing calculation and the poor applicability of local models, the present invention provides a method for coupling modeling of wellbore gravel packing and formation fracturing and gravel packing, which can construct a mathematical model for simulating the whole process of wellbore fracturing fluid flow, formation fracture propagation morphology, and gravel packing.

[0006] The present invention relates to a method for constructing an integrated model of deep - water high - temperature and high - pressure fracturing and packing based on wellbore / formation coupling. The method includes the following steps:

[0007] (1) Based on the improvement of the quasi - three - dimensional model of linear elastic fracture mechanics and / or the treatment of tip plasticity in the elastoplastic model and cohesive force model based on the Drucker - Prager yield criterion, construct a fracture propagation and extension model to obtain relevant data on fracture propagation and extension;

[0008] (2) For deep - water high - temperature and high - pressure conditions, construct a wellbore and fracture temperature field model;

[0009] (3) According to the relevant data on fracture propagation and extension in step (1), construct fracture filtration models for different formation types respectively;

[0010] (4) Based on the relevant data on fracture propagation and extension in step (1), construct a wellbore gravel packing model;

[0011] (5) Based on the relevant data on fracture propagation and extension in step (1), construct a pumping program design model to obtain the time data of the wellbore gravel packing model.

[0012] Among them, the relevant data on fracture propagation and extension in step (1) include fracture propagation pressure, fracture propagation time, and fracture volume change data.

[0013] Among them, in step (2), when the formation type is a brittle formation, construct a Carter filtration model applicable to the filtration and filter cake formation of cross - linked fracturing fluid in a high - permeability formation; when the formation type is a loose formation, a PDFL model applicable to the case of no filter cake for linear fracturing fluid.

[0014] Among them, for deep - water high - temperature and high - pressure conditions, in step (3), the wellbore and fracture temperature field model includes a seawater - section wellbore temperature calculation model, a formation - filling - section wellbore temperature calculation model, and a fracture temperature calculation model.

[0015] Among them, in step (4), the construction of the wellbore gravel packing part model includes a filling flow model and a friction calculation model. The filling flow model is constructed by the critical equilibrium flow velocity equation, sand - liquid mass balance equation, gravel mass balance equation, and sand - carrying fluid leakage rate equation; the friction calculation model includes friction calculation in the pipe string, friction calculation in the α - wave filling wellbore, and friction calculation in the β - wave filling wellbore.

[0016] Among them, the Nolte method is used to construct the pumping program design model.

[0017] Among them, the pumping program design model includes the start time of low sand ratio, the time to stop pumping low sand ratio, and sand ratio increment calculation.

[0018] Among them, the parameter transfer relationships in the five models are as follows: In the fracture propagation model, the fracturing fluid rheological parameters in the fracture filtration model are used to calculate and transfer the pressure data, and the fracture propagation time and fracture volume change data are transferred to the pumping design model. At the same time, the pressure data is provided for the calculation of the gravel packing model; the temperature field model provides temperature data for the calculation of the fracturing fluid rheological parameters in the fracture filtration model, and further transfers the rheological parameters to the fracture propagation model; the results of the fracture filtration model can be transferred to the continuity equation calculation in the fracture propagation model; the pumping design model transfers the time data of gravel packing to the wellbore gravel packing model.

[0019] Among them, the model coupling conditions are as follows:

[0020] Temperature: The bottom-hole temperature is equal to the fracture mouth temperature. T w = T f0

[0021] Pressure: The bottom-hole pressure is equal to the fracture mouth pressure. P w = P f0

[0022] Flow rate: The bottom-hole flow rate is equal to the fracture mouth flow rate. Q w = Q f0

[0023] Among them, the model adopted for the tip plasticity treatment in step (1) is the cohesive force model, and the tension-displacement relationship adopted is the bilinear model. The relationship is as follows:

[0024]

[0025] The advantages of the present invention are as follows:

[0026] 1. The present invention realizes the construction of a model for the coupling of wellbore gravel packing and formation fracturing packing, and can simulate the whole process of fracturing packing.

[0027] 2. The present invention can timely select the fracture propagation model according to the formation conditions and select the filtration model according to the fracturing fluid conditions. It is an integration of various models for fracturing packing and has the advantage of universality.

[0028] 3. The model construction method of the present invention fully considers temperature alternation, the rheological and filtration properties of fracturing fluid, and different formation conditions, and the simulation results are more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the flow chart of the construction of the integrated model for deepwater high-temperature and high-pressure fracturing packing based on wellbore / formation coupling of the present invention.

[0030] Figure 2 is the flow chart of fracture propagation calculation in Embodiment 2 of the present invention.

[0031] Figure 3 For Experimental Example 3 of the present invention, the temperature change of the filling fluid in the wellbore with different pump displacements was calculated.

[0032] Figure 4 The friction resistance of each part in the present invention changes with time. Detailed implementation manners

[0033] The present invention will be described in detail below through specific embodiments in conjunction with the accompanying drawings, but it is not limited thereto. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0034] The technical solution of the present invention is as follows:

[0035] A method for constructing an integrated model of deep-water high-temperature and high-pressure fracturing and filling based on wellbore / formation coupling includes the following steps:

[0036] (1) Construct a calculation model for fracture propagation and extension

[0037] The propagation of fractures mainly includes the extension of fractures before tip screen-out and the width expansion of fractures after tip screen-out. The construction of the fracture propagation and extension model in the present invention is mainly through two methods: one is the improvement of the quasi-three-dimensional model based on linear elastic fracture mechanics, and the other is the treatment of tip plasticity by the elastoplastic model and cohesive force model based on the Drucker-Prager yield criterion, which is applicable to the simulation of fracturing fractures in various formation conditions such as brittle and plastic.

[0038] (1.1) Fracture propagation and extension before tip screen-out

[0039] The calculation method of the fracture shape before tip screen-out in the present invention is constructed by four equations, including the fracture width equation, fracture pressure drop equation, fracture height equation, and continuity equation. The main parameters: w is the fracture width, h is the fracture height, p is the pressure, q is the flow rate. λ(x, t) is the filtration velocity, which is given by the filtration model. v is the Poisson's ratio, and E is the elastic modulus.

[0040] ① Fracture width equation:

[0041] The fracture width is mainly affected by the pressure in the fracture and the rock properties.

[0042] When the fracture extends in the pay zone and has not reached the upper and lower barrier layers:

[0043]

[0044] The width distribution of the fracture in the height direction has reached the upper and lower barrier layers

[0045]

[0046] The general functional form of the width equation is:

[0047] w(x, z, t) = f1[p(x, z, t), h(x, t)]

[0048] where u and τ are integration variables; y is the axis in the fracture height direction; where H p is the reservoir thickness.

[0049] ② Pressure drop equation:

[0050] The pressure drop calculation method in the present invention is obtained according to the pressure drop equation with the pipeline shape factor of Notle. The pressure drop of fluid flow at a certain position is:

[0051]

[0052] The form of the pipeline shape factor is:

[0053]

[0054] The general form of the pressure drop equation:

[0055]

[0056] where K is the consistency coefficient, Pa·s n ; n is the rheological index, dimensionless. z is the integration variable.

[0057] ③ Height equation:

[0058] In the present invention, for reservoirs with small brittle and plastic zones, the following Rice stress intensity factor K I formula (including other improved forms) is used. For reservoirs with large plastic deformation, an elastoplastic model based on the Drucker-Prager yield criterion and the following cohesive force model are used to handle the tip plasticity.

[0059]

[0060] The general form of the width equation:

[0061] f3(p(x), h(x)) = 0

[0062] ④ Continuity equation:

[0063] Part of the fracturing fluid is used to create fractures in the formation, and part of it filtrates into the formation. According to the principle of mass conservation, the change in flow rate in the vertical cross-section of the fracture is equal to the sum of the filtration velocity of the fluid per unit fracture length and the change rate of the vertical cross-sectional area, where A is the vertical cross-sectional area of the fracture.

[0064]

[0065] The filtration velocity, as the result of the filtration model, can be transferred to the calculation of the continuity equation in the fracture propagation model.

[0066] ⑤ Tip plasticity treatment:

[0067] In the present invention, the cohesion model is used to deal with the nonlinearity of tip plasticity for plastic formations. The tension-displacement relationship adopts a bilinear model. As the opening amount increases, the cohesion increases linearly. At the critical point of the opening amount (Δ el ), it reaches the maximum tensile strength (T max ). At this time, microcracks begin to generate. After that, the cohesion decreases with the increase of the opening amount until it disappears and the interface is completely separated (Δ IC ), and the fracture begins to propagate. The area enclosed by the tension-displacement curve is equal to the fracture energy. The relationship between the fracture energy G IC and the rock fracture toughness K IC is as follows.

[0068]

[0069] (1.2) Fracture propagation and extension after sand-out

[0070] After sand-out, the fracture length and fracture height no longer change. Therefore, in the present invention, the construction of the fracture propagation model is mainly through the fracture width equation. The fracture width equation is directly related to the pressure in the fracture, and the change in pressure is related to the change in fracture volume and the filtration of the fracturing fluid. During calculation, the fracture length is divided into several segments from the fracture tip to the well bottom. By assuming the flow rate at each cross-section i, the volume increment of each segment of the fracture is obtained, and then the fracture width of this segment is solved. Through the principle of material balance, it is compared with the calculated volume increment for iterative calculation until the calculation accuracy requirement is met. The main equations used for construction are as follows.

[0071] ① Fracture width equation:

[0072]

[0073] ② Fracture filtration equation:

[0074]

[0075] ③ Volume increase equation:

[0076]

[0077] ④ Fracture pressure drop equation:

[0078]

[0079] ΔV l is the filtrate volume; T so is the end - sand - out time; where t n is the nth moment after sand - out; ΔV f is the change in fracture volume; C L is the filtrate coefficient; A is the fracture area.

[0080] (2) Construct the wellbore and fracture temperature field model

[0081] The present invention relates to deep - water high - temperature and high - pressure reservoirs. The fluid experiences a temperature alternating process from the wellhead to the formation. Therefore, the temperature field model is an important part of the present invention. The temperature field model is mainly divided into three parts: one is the wellbore temperature calculation model in the seawater section; the second is the wellbore temperature calculation model in the formation filling section; the third is the fracture temperature calculation model.

[0082] (2.1) Wellbore mortar temperature calculation model in the seawater section

[0083]

[0084] In the formula: Q c is the heat source term, which is the work done by the control volume per unit time and per unit length; ρ l , q, C l are the fluid density, flow rate and specific heat capacity respectively, r ci is the inner diameter of the pipe string, T w , T c are the inner wall temperature of the pipe string and the liquid temperature respectively; h ci is the convective heat transfer coefficient between the pipe wall and the liquid.

[0085] (2.2) Temperature calculation model in the filling section

[0086]

[0087] In the formula: ρl, q, C l are the fluid density, flow rate and specific heat capacity respectively, T a , T s and T cw are the annulus liquid temperature, formation temperature and outside wall temperature of the wash pipe respectively, r w , r co are the wellbore radius and the outside radius of the wash pipe respectively, h w and h co are the convective heat transfer coefficients between the wellbore wall, the outside wall of the wash pipe and the annulus liquid respectively.

[0088] (2.3) Fracture Temperature Calculation Model

[0089] The temperature calculation method in the fracture is mainly derived from the continuity equation, the energy conservation equation, and the filtration zone and rock energy equation. Specific method: First, integrate and add the continuity equation and the fluid energy conservation equation along the fracture height direction, and use the Laplace integral transform for the rock energy equation. Divide the fracture along the fracture length and use the difference method to calculate and solve. The temperature calculation results can be output to the fracturing fluid filtration parameters and rheological parameters.

[0090] ① Continuity equation of fluid in the fracture:

[0091]

[0092] ② Energy conservation equation of fluid in the fracture:

[0093]

[0094] ③ Energy equation of the filtration zone:

[0095]

[0096] (pC) ef =φρ f C f +(1 - φ)ρ r C r

[0097] K ef =φK f +(1 - φ)K r

[0098] ④ Rock energy equation:

[0099]

[0100] In the formula, u is the liquid flow velocity at the average fracture width; λ is the filtration velocity; γ is the heat transfer coefficient; T f is the temperature in the fracture; ρ f is the liquid density; C f is the specific heat of the liquid; ρ r is the formation rock density; C r is the specific heat of the formation rock; T rw is the temperature of the fracture wall rock; δ is the thickness of the filtration zone; K f is the liquid thermal conductivity; K r is the formation rock thermal conductivity.

[0101] (3) Construct a fracture filtration model

[0102] The construction of the filtration loss model mainly applies some classic models. For different fracturing fluids and formation conditions, two calculation models are provided in the present invention. They are the Carter filtration loss model (brittle formation) applicable to the filtration loss and filter cake formation of crosslinked fracturing fluids in high-permeability formations, and the PDFL model (unconsolidated formation) applicable to the case of linear fracturing fluids without filter cake.

[0103] (3.1) Carter filtration loss model

[0104]

[0105] λ is the filtration loss velocity; C is the comprehensive filtration loss coefficient; t is the filtration loss time; τ(x) is the time when filtration loss starts at x.

[0106] (3.2) PDFL model (pressure-related)

[0107]

[0108] The filtration loss velocity is related to the rheology of the fracturing fluid, pressure, compressibility of the reservoir fluid, and interface position parameters.

[0109] Among them, k is the formation permeability, μ app is the apparent viscosity of the fracturing fluid, φ is the formation porosity, ξ is a constant related to the interface position, where c t is the total compressibility of the fracturing invasion zone.

[0110] The solution of the two filtration loss models: The solution of the Carter filtration loss model is relatively simple and can be directly solved. Only the comprehensive compressibility coefficient and the filtration loss time need to be determined. The comprehensive compressibility coefficient is related to rock mechanics parameters as well as pressure and temperature data, and the pressure and temperature data can be calculated and provided by the fracture propagation model and the temperature field model.

[0111] The PDFL model is suitable for the case where filter cake is generated. It is necessary to input the fracture size parameters (i.e., the length, width, and height of the fracture obtained in step 1), which can be provided by the fracture propagation model. At the same time, the rheological parameters of the fracturing fluid, as well as the mechanical parameters and interface position parameters of the formation, are also required. It can be solved iteratively. The calculation results of the filtration loss model can be applied to the continuity equation of the fracture model.

[0112] (4) Construction of the wellbore gravel packing model

[0113] The present invention relates to the coupled calculation of wellbore gravel packing and formation fracturing packing. The construction of the wellbore gravel packing part model is mainly divided into two parts: one is the filling flow model, which is mainly constructed by the critical equilibrium flow velocity equation, sand-fluid mass balance equation, gravel mass balance equation, and sand-carrying fluid leakage rate equation; the other is the friction calculation model, which is mainly divided into friction calculation in the pipe string, friction calculation in the α-wave filling wellbore, and friction calculation in the β-wave filling wellbore.

[0114] (4.1) Filling flow model

[0115] ① Critical equilibrium flow velocity equation:

[0116]

[0117] ② Sand - liquid mass balance equation:

[0118] (1 - Ci)ρq i -(1 - C * )ρq * -ρq tp -ρq Ls = 0

[0119] ③ Gravel mass balance equation:

[0120] C i q i -C * q * = 0

[0121] ④ Leakage rate equation of sand - carrying fluid:

[0122]

[0123] Where: v * 、v s are the equilibrium flow velocity and the gravel particle settlement velocity respectively, m / s; r H 、d p are the hydraulic diameter and the gravel particle diameter respectively, m; ρ l 、ρ p are the density of the sand - carrying fluid and the gravel particle respectively, kg / m 3 ; μ l - the viscosity of the sand - carrying fluid, Pa·s; C * - the volume concentration of gravel particles under equilibrium conditions, m 3 / m 3 ; C i 、C * are the initial injected gravel volume concentration and the volume concentration of gravel above the equilibrium dike, m 3 / m 3 ; q i 、q * 、q tp 、q Ls are the initial injection displacement of the mortar, the mortar flow rate above the equilibrium dike, the pure sand - carrying fluid flow rate in the screen - washing annulus, and the filtration loss of the sand - carrying fluid into the formation respectively, m 3 / s; K h 、K v are the horizontal permeability and vertical permeability of the formation respectively, μm 2; h and L are the thickness and horizontal length of the oil layer respectively, in m; P w and P e are the wellbore pressure and the pressure at the boundary respectively, in MPa; μ0 is the viscosity of the formation crude oil, in mPa·s; r w and r e are the wellbore radius and the supply edge radius respectively, in m.

[0124] (4.2) Friction calculation model

[0125] ① Friction calculation equation in the pipe string:

[0126]

[0127] ② Friction calculation equation in the wellbore filled with α wave:

[0128]

[0129] ③ Friction calculation equation in the wellbore filled with β wave:

[0130]

[0131] In the formula: L inj (t) is the length of the mortar flowing through at time t; Q p - Pump displacement; D intcol - Inner diameter of the pipe string; ΔP colinj-t Friction pressure drop above the casing shoe during the injection stage; ρ mix and ρ f - Are the densities of the mortar and the completion fluid respectively;

[0132] L cs - Depth at the casing shoe; f - Friction coefficient; ΔP oh，inj - Friction in the horizontal section during the injection stage; L oh - Horizontal wellbore length; A an and D h - Are the cross-sectional area and hydraulic diameter of the wellbore annulus respectively; L α (t) is the distance of the α wave front at time t; C mix - Mortar concentration; A low and φ - Represent the cross-sectional area and porosity of the bottom sand bed respectively;

[0133] D hup and D han - Represent the hydraulic diameters of the upper part of the α sand bed and the wellbore annulus respectively; A up - Flow-through area of the upper part of the α sand bed; ΔP oh，β - Wellbore friction pressure drop during the β wave filling stage; L β (t) is the distance of the β wave front at time t;

[0134] D int，scr, D ext，w- respectively represent the inner diameter of the screen pipe and the outer diameter of the flush pipe.

[0135] (5) Construct a pumping program design model

[0136] The pumping program guides the fracturing and packing process, mainly including low sand ratio injection, high sand ratio injection, and sand separation process.

[0137] (5.1) Low sand ratio start time:

[0138] The liquid efficiency e so and the geometric size of the fracture at the time t so when the sand separation time t is calculated by the fracture propagation model are provided. The Nolte calculation method is adopted:

[0139] PF = (1 - e s0 ) 2 + SF

[0140] PF is the ratio of the preflush fluid to the total fluid volume; SF is the safety margin, generally about 0.03 can be taken.

[0141] The time when the low sand ratio sand-carrying fluid starts to be pumped is:

[0142] t LS = t so PF

[0143] (5.2) The time t ms

[0144] when the first batch of high sand ratio sand-carrying fluid reaches the fracture tip is the time t ms at the end of the sand separation construction at the tip: t eoj : t ms = t eoj [(1 - e eoj ) 2 + SF]

[0145] t ms and the difference between t LS is the time when the low sand ratio fluid is pumped.

[0146] (5.3) Sand ratio increment calculation: The Nolte method is adopted:

[0147] C d (τ) = C dmax τ α ,

[0148] τ = (t - t ms ) / (t eoj - t ms ),

[0149] α = (1 - eeoj -F d / e eoj )

[0150] where C d (τ) is the proppant concentration of dimensionless time, C dmax is the highest proppant concentration, α is the working fluid efficiency, F d is the proppant fluid shape factor.

[0151] Total proppant dosage pumped in:

[0152] M = QP(t θoj -t ms )C dmax / (1 + α)

[0153] (6) Coupling conditions

[0154] The coupling conditions are settings in the calculation process, specifically including the following three points: First, when making the temperature calculation model, the bottom hole temperature is the same as the fracture mouth temperature. Second, when making the fracture propagation model calculation, the fracture mouth pressure is the bottom hole pressure calculated by the wellbore gravel packing model. Third, when making the flow rate calculation, the bottom hole flow rate is equal to the fracture mouth flow rate.

[0155] In the present invention, the coupling conditions between the wellbore and the bottom hole are real-time, for each moment of fracturing and packing:

[0156] Temperature: The bottom hole temperature is equal to the fracture mouth temperature.

[0157] T w = T f0

[0158] Pressure: The bottom hole pressure is equal to the fracture mouth pressure.

[0159] P w = P f0

[0160] Flow rate: The bottom hole flow rate is equal to the fracture mouth flow rate.

[0161] Q w = Q f0

[0162] Example 1: Refer to Figure 1 , a method for constructing an integrated model of deepwater high-temperature and high-pressure fracturing and packing based on wellbore / formation coupling, comprising the following steps:

[0163] (1) Construction of fracture propagation model: Construct a fracture propagation calculation model through the aforementioned model construction method. The main input data are: formation parameters, preset fracture length, rheological mode, pump displacement, and stimulation ratio. The main output data are: the length, width, height, and pressure distribution of the fracture at each moment before and after sand-out. The fracture propagation model calculates and transfers pressure data for the rheological parameters of the fracturing fluid, transfers fracture propagation time and fracture volume change data to the pumping design model, and provides pressure data for the calculation of the gravel packing model at the same time.

[0164] (2) Construction of temperature field model: Construct a temperature field calculation model through the aforementioned model construction method. The main input data are: parameters such as seawater temperature specific heat capacity, fracture length, wellbore parameters, and formation parameters. The main output data are: the temperature distribution along the wellbore and fracture at each moment. The temperature field model provides temperature data for the calculation of the rheological parameters of the fracturing fluid, and further transfers the rheological parameters to the fracture propagation model (refer to Figure 1 , different rheological parameters correspond to different temperatures, which, together with pressure, are used as influencing conditions for the rheological parameters).

[0165] (3) Construction of filtration model: Construct a filtration calculation model through the aforementioned model construction method. The main input data are: rheological parameters of the fracturing fluid (refer to Figure 1 , the rheological parameters are determined by temperature and pressure, the temperature is obtained from the temperature field calculation, and the pressure is obtained from the fracture propagation calculation model. It should be noted that mutual iteration and coupling occur throughout the process) and filtration coefficient. The main output data are: the filtration velocity at each moment and position. The results can be transferred to the calculation of the continuity equation in the fracture propagation model.

[0166] (4) Construction of pumping design model: Construct a pumping design calculation model through the aforementioned model construction method. The main input data are: preset fracture length, sand-out moment, and fracturing fluid efficiency. The main output data are: injection times of preflush fluid, low sand ratio, and high sand ratio; sand-out time; fracturing fluid consumption. It can transfer the time data of gravel packing to the wellbore gravel packing model.

[0167] (5) Construction of wellbore gravel packing model: Construct a gravel packing calculation model through the aforementioned model construction method. The main input data are: preset formation parameters, wellbore parameters, and sand-carrying fluid parameters. The main output parameters are: wellbore friction, wellbore pressure, and sand-carrying fluid flow parameters.

[0168] Example 2: Refer to Figure 2 , this example gives a method for calculating the fracture shape using the fracture propagation model. The steps are as follows:

[0169] (1) Preset the fracture length at a certain moment, and the sand-out moment can be determined accordingly.

[0170] (2) Assume the production of each section after fracturing, and the final fracture width can be determined from the relationship between the fracture width and the stimulation ratio.

[0171] (3) Based on the derivation of the fracture height equation and the pressure drop equation of the fracture propagation model before sand-out, the final fracture height can be determined. Determine the filtration rate according to the filtration model, further determine the fracture width through the fracture width equation, and calculate the cross-sectional area A. Re-determine the flow rate of each section according to the continuity equation and compare it with the assumed flow rate until the accuracy is satisfied to obtain the change in the fracture shape before sand-out. At the same time, determine the pressure drop, injection volume, and fracturing fluid efficiency.

[0172] (4) According to the final fracture length, fracture height, and the fracture propagation model after sand-out, the change in the fracture width can be determined, as well as the pressure drop, injection volume, and fracturing fluid efficiency during the high sand ratio filling process after sand-out. At the same time, the final pressure drop can be determined.

[0173] (5) Check the upper limit of the pressure drop in the wellbore. If it meets the requirements, output the results; if not, re-assume the production after fracturing and repeat the above process.

[0174] Example 3: Calculate the deep wellbore temperature using the temperature model calculation method of the present invention

[0175] In this example, the deep wellbore temperature is calculated using the temperature model calculation method of the present invention. The results are as Figure 3 shown, and the specific steps are as follows:

[0176] (1) Select different pump displacement rates, 4.5 bpm to 7.0 bpm.

[0177] (2) Calculate the wellbore temperature using the following seawater section wellbore slurry temperature calculation model and filling section temperature calculation model.

[0178]

[0179]

[0180] (3) Compare the changes in the deep water environment wellbore temperature under different pump displacement rates to provide parameters for other model parts. It can be seen from Figure 3 that: in the cooling stage (<1500 m), the smaller the displacement rate, the lower the temperature; in the heating stage (>1500 m), the situation is exactly the opposite.

[0181] The variation law of the friction resistance of each part with time is as Figure 4 shown. The friction resistance calculation method includes the following steps:

[0182] (1) Select a horizontal well and input parameters such as the wellbore, sand-carrying fluid, and pump displacement rate.

[0183] (2) Calculate the friction resistance of each part according to the friction resistance calculation method in the gravel packing model.

[0184] (3) Compare the variation trends of the frictions of each part with the packing time to provide guidance for the gravel packing in the wellbore.

[0185] The above has described the present invention in detail. For those skilled in the art, without departing from the gist and scope of the present invention and without the need for unnecessary experiments, the present invention can be implemented within a relatively wide range under equivalent parameters, concentrations and conditions. Although specific embodiments of the present invention are given, it should be understood that the present invention can be further improved. In short, according to the principle of the present invention, this application is intended to cover any modification, use or improvement of the present invention, including those that depart from the scope disclosed in this application and are made with conventional techniques known in the art. The application of some basic features can be made according to the scope of the appended claims below.

Claims

1. A method for constructing an integrated model of deepwater high-temperature and high-pressure fracturing and packing based on wellbore / formation coupling, characterized in that It includes the following steps: (1) Based on the improvement of the quasi-three-dimensional model of linear elastic fracture mechanics, the elastoplastic model based on the Drucker-Prager yield criterion, and the treatment of tip plasticity by the cohesive force model, a crack propagation and extension model is constructed to obtain the relevant data of crack propagation and extension; (2) A wellbore and crack temperature field model is constructed for deepwater high-temperature and high-pressure conditions; (3) According to the relevant data of crack propagation and extension in step (1), crack filtration models are constructed respectively according to different formation types; (4) Based on the relevant data of crack propagation and extension in step (1), a wellbore gravel packing model is constructed; (5) Based on the relevant data of crack propagation and extension in step (1), a pumping program design model is constructed to obtain the time data of the wellbore gravel packing model; Among them, the crack propagation model calculates and transmits the pressure data of the fracturing fluid rheological parameters in the crack filtration model, transmits the crack propagation time and crack volume change data to the pumping design model, and provides pressure data for the calculation of the gravel packing model at the same time; the temperature field model provides temperature data for the calculation of the fracturing fluid rheological parameters in the crack filtration model, and further transmits the rheological parameters to the crack propagation model; the result of the crack filtration model can be transmitted to the continuity equation calculation in the crack propagation model; the pumping design model transmits the time data of gravel packing to the wellbore gravel packing model.

2. A method for constructing an integrated model of deepwater high-temperature and high-pressure fracturing and packing based on wellbore / formation coupling according to claim 1, characterized in that The relevant data of crack propagation and extension in step (1) include crack propagation pressure, crack propagation time, and crack volume change data.

3. A method for constructing an integrated model of deepwater high-temperature and high-pressure fracturing and packing based on wellbore / formation coupling according to claim 1, characterized in that, In step (3), when the formation type is a brittle formation, a Carter filtration model applicable to the filtration and cake formation of crosslinked fracturing fluid in high-permeability formations is constructed; when the formation type is a loose formation, a PDFL model applicable to the case of no cake formation of linear fracturing fluid is used.

4. A method for constructing an integrated model of deepwater high-temperature and high-pressure fracturing and packing based on wellbore / formation coupling, characterized in that, For deepwater high-temperature and high-pressure conditions, in step (2), the wellbore and crack temperature field model includes a seawater section wellbore temperature calculation model, a formation filling section wellbore temperature calculation model, and a crack temperature calculation model.

5. A method for constructing an integrated model of deepwater high-temperature and high-pressure fracturing and packing based on wellbore / formation coupling, characterized in that, In step (4), the construction of the wellbore gravel packing partial model includes a filling flow model and a friction calculation model. The filling flow model is constructed by the critical equilibrium flow velocity equation, the sand-liquid mass balance equation, the gravel mass balance equation, and the sand-carrying fluid leakage rate equation; the friction calculation model includes the friction calculation inside the pipe string, the friction calculation in the α-wave filling wellbore, and the friction calculation in the β-wave filling wellbore.

6. A method for constructing an integrated model of deepwater high-temperature and high-pressure fracturing and packing based on wellbore / formation coupling, characterized in that, The Nolte method is used to construct the pumping program design model.

7. A method for constructing an integrated model of deepwater high-temperature and high-pressure fracturing and packing based on wellbore / formation coupling, characterized in that, The pumping program design model includes the start time of the low sand ratio, the time to stop pumping the low sand ratio, and the sand ratio increment calculation.

8. A method for constructing an integrated model of deepwater high-temperature and high-pressure fracturing and packing based on wellbore / formation coupling according to any one of claims 1-7, characterized in that, The model coupling conditions in the model construction process are: Temperature: The bottom-hole temperature is equal to the fracture mouth temperature, ; Pressure: The bottom-hole pressure is equal to the fracture mouth pressure, ; Flow rate: The bottom-hole flow rate is equal to the fracture orifice flow rate, .

Images